Asphalt shingles are composed of a base material, either organic felt or glass-fiber mat, that provides support for weather-resistant components and gives a shingle strength. Asphalt, fillers and surfacing material generally in the form of mineral granules, provide protection from impact/UV degradation and improve fire resistance.
The most common form of asphalt shingles are strip shingles. They are rectangular with the most prevalent size being 12 in. wide by 36 in. long. Metric shingles are 13 1/4 in. wide by 39 3/8 in. long. Shingles may be produced in a single layer or two or more layers. The latter generally are referred to as architectural shingles or laminated strip shingles and they have a three dimensional appearance.
Both 3-tab asphalt shingles and laminated asphalt shingles contain a strip of factory applied adhesive that is activated by the sun's heat after installation and seals each shingle to the next course. The seal strip also provides much of a shingle's resistance to wind uplift. Shingles with factory-applied adhesive have a strip of clear polyester film applied to each shingle to prevent the sealing strips from bonding the shingles together when packaged. When the shingles are installed, the self-sealing strips will not align with the plastic film strips and will bond to adjacent shingles. For this reason, the plastic film strips do not have to be removed.